REFLECTOR: Brake shudder - RG

John Dibble aminetech at bluefrog.com
Mon Dec 4 11:07:03 CST 2006


I've milled the rotors with limited success.  I have also discovered
that the attach holes in my rotors are not perfectly concentric.  I
discovered this when I watched them milling the rotors, the wear area
had a slight wobble as it turned on the mill.  Matco told me that there
was a period in the late '90s when the holes were drilled by hand and
may have resulted in them not being perfect.  I replaced with new
rotors.  I got further improvement, but still some shudder, at very low
speeds.  It's manageable as long as I don't need to brake hard at the
end of the roll.  I haven't changed my bolts and perhaps that will offer
further improvement.  However I have no front to back play when I have
it jacked up off the groung.

John

Al Gietzen wrote:

> After the first few landings with the Matco brakes, I began to get
> ‘shudder’ of the main gear somewhere in the 40 – 30 kt range when
> applying the brakes on roll out.  This can be annoying, as well as
> cause a pretty good shake of the plane.  I’m told this is common with
> Velocitys.  There is a point of resonance involved here, and there
> must be a driving force.
>
> I recall someone posted here about just a few mils distortion of the
> rotors causing this, and milling the rotors true solved the problem.
> Do I recall correctly, and did the problem stay solved?  Where/how did
> you get them trued up?
>
> While investigating the issue, I found that the retracted position now
> the gear is about 1/8 – 3/16” further forward in the wells, which
> eliminated the clearance of the gear doors to the stake opening.  Is
> this a common occurrence?  I thought that perhaps the pivot bolts on
> my 1996 kit were not grade 8 and may be bent a bit, but they were
> grade 8.  I changed them out anyway, and found it eliminated a bit of
> play.  Examining the bolts shows that they were not very round, and
> the high spots were worn.  I think the new bolts are more true.
>
> I also noted there was now about .010 - .015” fore-aft movement of the
> gear (the spacers originally fit very close), and the bolts were
> loosely tightened to allow them to rotate in the bushings, rather than
> the sleeve in the leg rotating on the bolts.  When I installed the new
> bolts I tightened them a bit more which reduced the clearance, but
> will mean that the bolts will not rotate in the bushings.  Any opinion
> on whether it matters?
>
> Thanks,
>
> Al
>
> Thanks,
>
> All
>
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